The present invention relates to a method of producing a magnetoresistance effect film and a magnetoresistance effect film.
It is known that a magnetoresistance effect film having an insulating barrier layer composed of MgO has a great magnetoresistance (MR) ratio (see S. Yuasa et al., Nat. Mater. 3(2004)868; S. S. P. Parkin et al., Nat. Mater. 3(2004)862; and D. D. Djayaprawira et al., 230% room-temperature magnetoresistance in CoFeB/MgO/CoFeB mangentic tunnel junctions, Appl. Phys. Lett. 86(2005)092502). Because MgO has crystal orientation of (200), the MgO barrier layer has the great MR ratio.
TMR heads including the MgO barrier layers have high reproduction sensitivities, so they can be suitably used for magnetic heads and magnetic memory storages for high density recording. However, with increasing recording densities, magnetoresistance effect elements for reading signals must process signals at high speed. To increase signal transmitting speeds, resistance values of the magnetoresistance effect elements must be reduced. On the other hand, the magnetoresistance effect elements must be downsized so as to correspond to high recording densities. If the magnetoresistance effect elements are downsized without thinning barrier layers, resistance values of the barrier layers must be increased. Namely, the barrier layers must be thinned so as to downsize the magnetoresistance effect elements without at least varying the resistance values.
As described above, in the magnetoresistance effect elements having the barrier layers, the barrier layers must be thinner so as to downsize the magnetoresistance effect elements with maintaining the resistance values. However, if the barrier layers are thinned, crystal orientation of the barrier layers will be deteriorated and characteristics of the magnetoresistance effect elements, e.g., MR ratio, will be worsened.
Note that, a laminated structure, in which the barrier layer is sandwiched between a pinned magnetic layer, whose magnetization direction is fixed, and a free magnetic layer, whose magnetization direction is rotated by external magnetic fields, can be used for not only a part of the magnetoresistance effect element but also a part of a magnetoresistance device, e.g., M-RAM.